Method for hot swapping of network components

ABSTRACT

Methods of removing and replacing data processing circuitry are provided comprising removing a network interface module from the computer without powering down the computer and removing an interface card from the network interface module. The further acts of replacing the interface card into the network interface module and replacing the network interface module into the computer without powering down the network computer are also performed in accordance with this method.

PRIORITY CLAIM

The benefit under 35 U.S.C. § 119(e) of the following U.S. provisionalapplication(s) is hereby claimed:

Application Title No. Filing Date “Hardware and Software Architecturefor 60/047,016 May 13, 1997 Inter-Connecting an Environmental Man-agement System with a Remote Interface” “Self Management Protocol for aFly-By- 60/046,416 May 13, 1997 Wire Service Processor” “IsolatedInterrupt Structure for Input/ 60/047,003 May 13, 1997 OutputArchitecture” “Three Bus Server Architecture with a 60/046,490 May 13,1997 Legacy PCI Bus and Mirrored I/O PCI Buses” “Computer SystemHardware Infra- 60/046,398 May 13, 1997 structure for Hot PluggingSingle and Multi-Function PC Cards Without Embedded Bridges” “ComputerSystem Hardware Infra- 60/046,312 May 13, 1997 structure for HotPlugging Multi-Function PCI Cards With Embedded Bridges”

RELATED APPLICATIONS

The subject matter of U.S. patent application entitled “FAULT TOLERANTCOMPUTER SYSTEM”, filed on Oct. 1, 1997, application Ser. No.08/942,194, is related to this application.

APPENDICES

Appendix A, which forms a part of this disclosure, is a list of commonlyowned copending U.S. patent applications. Each one of the applicationslisted in Appendix A is hereby incorporated herein in its entirety byreference thereto.

COPYRIGHT RIGHTS

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files of records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

Network servers and the accompanying local area networks (LANs) haveexpanded the power and increased the productivity of the work force. Itwas just a few years ago that every work station had a standalonepersonal computer incapable of communicating with any other computers inthe office. Data had to be carried from person to person by diskette.Applications had to be purchased for each standalone personal computerat great expense. Capital intensive hardware such as printers wereduplicated for each standalone personal computer. Security and backingup the data were immensely difficult without centralization.

Network servers and their LANs addressed many of these issues. Networkservers allow for resource sharing such as sharing equipment,applications, data, and the means for handling data. Centralized backupand security were seen as definite advantages. Furthermore, networksoffered new services such as electronic mail. However, it soon becameclear that the network servers could have their disadvantages as well.

Centralization, hailed as a solution, developed its own problems. Apredicament that might shut down a single standalone personal computerwould, in a centralized network, shut down all the networked workstations. Small difficulties easily get magnified with centralization,as is the case with the failure of a network server interface card(NIC), a common dilemma. A NIC may be a card configured for Ethernet,LAN, or Token-Ring to name but a few. These cards fail occasionallyrequiring examination, repair, or even replacement. Unfortunately, theentire network has to be powered down in order to remove, replace orexamine a NIC. Since it is not uncommon for modern network servers tohave sixteen or more NICs, the frequency of the problem compounds alongwith the consequences. When the network server is down, none of theworkstations in the office network system will be able to access thecentralized data and centralized applications. Moreover, even if onlythe data or only the application is centralized, a work station willsuffer decreased performance.

Frequent down times can be extremely expensive in many ways. When thenetwork server is down, worker productivity comes to a stand still.There is no sharing of data, applications or equipment such as spreadsheets, word processors, and printers. Bills cannot go out and orderscannot be entered. Sales and customer service representatives are unableto obtain product information or pull up invoices. Customers browsing orhoping to browse through a network server supported commercial web pageare abruptly cut off or are unable to access the web pages. Suchfrustrations may manifest themselves in the permanent loss of customers,or at the least, in the lowering of consumer opinion with regard to avendor, a vendor's product, or a vendor's service. Certainly, down timefor a vendor's network server will reflect badly upon the vendor'sreliability. Furthermore, the vendor will have to pay for more servicecalls. Rebooting a network server, after all, does require a certainamount of expertise. Overall, whenever the network server has to shutdown, it costs the owner both time and money, and each server shut downmay have ramifications far into the future. The magnitude of thisproblem is evidenced by the great cost that owners of network serversare willing to absorb in order to avoid down time through the purchaseof uninterruptible power supplies, surge protects, and redundant harddrives.

What is needed to address these problems is an apparatus that canlocalize and isolate the problem module from the rest of the networkserver and allow for the removal and replacement of the problem modulewithout powering down the network server.

SUMMARY OF THE INVENTION

The present invention includes methods of removing and replacing dataprocessing circuitry. In one embodiment, the method comprises changingan interface card in a computer comprising removing a network interfacemodule from the computer without powering down the computer and removingan interface card from the network interface module. The further acts ofreplacing the interface card into the network interface module andreplacing the network interface module into the computer withoutpowering down the network computer are also performed in accordance withthis method.

Methods of making hot swappable network servers are also provided. Forexample, one embodiment comprises a method of electrically coupling acentral processing unit of a network server to a plurality of networkinterface modules comprising the acts of routing an I/O bus having afirst format from the central processing unit to primary sides of aplurality of bus adaptor chips and routing an I/O bus of the same firstformat from a secondary side of the bus adaptor chips to respective onesof the network interface modules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a network server in accordance with theinvention including a fault tolerant computer system mounted on a rack.

FIG. 2 is a block diagram illustrating certain components and subsystemsof the fault tolerant computer system shown in FIG. 1.

FIG. 3A shows the chassis with network interface modules and powermodules.

FIG. 3B is an exploded view which shows the chassis and theinterconnection assembly module.

FIG. 3C is an illustration of the interconnection assembly module ofFIG. 3B.

FIG. 4 shows a front view of an embodiment of a network server in achassis mounted on a rack.

FIG. 5A is a view showing the front of the backplane printed circuitboard of an interconnection assembly module in the network server.

FIG. 5B is a view showing the back of the backplane printed circuitboard of the interconnection assembly module in the network server.

FIG. 6 is an exploded view which shows the elements of one embodiment ofa network interface module of the network server.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying Figures, wherein like numerals refer tolike elements throughout. The terminology used in the descriptionpresented herein is intended to be interpreted in its broadestreasonable manner, even though it is being utilized in conjunction witha detailed description of certain specific embodiments of the presentinvention. This is further emphasized below with respect to someparticular terms used herein. Any terminology intended to be interpretedby the reader in any restricted manner will be overtly and specificallydefined as such in this specification.

FIG. 1 shows one embodiment of a network server 100. It will beappreciated that a network server 100 which incorporates the presentinvention may take many alternative configurations, and may include manyoptional components currently used by those in the art. A specificexample of one such configuration is described in conjunction with FIG.1. The operation of those portions of the server 100 which areconventional are not described in detail.

In the server of FIG. 1, a cabinet 101 houses a rack 102, on which ismounted several data processing, storage, and display components. Theserver 100 may include, for example, a display monitor 173A resting on amonitor shelf 173B mounted on the rack 102 as well as a retractablekeyboard 174. Also included are a variable number of data storagedevices 106, which may be removably mounted onto shelves 172 of the rack102. One embodiment as shown in FIG. 1 has twenty data storage modules106 removably mounted individually on four shelves 172 of the rack 102,with five data storage modules 106 per shelf. A data storage module maycomprise magnetic, optical, or any other type of data storage media. Inthe embodiment illustrated in FIG. 1, one data storage module is aCD-ROM module 108.

In advantageous embodiments described in detail with reference to FIGS.2-6 below, the network server includes a fault tolerant computer systemwhich is mounted in a chassis 170 on the rack 102. To provide previouslyunavailable ease in maintenance and reliability, the computer system maybe constructed in a modular fashion, including a CPU module 103, aplurality of network interface modules 104, and a plurality of powermodules 105. Faults in individual modules may be isolated and repairedwithout disrupting the operation of the remainder of the server 100.

Referring now to FIG. 2, a block diagram illustrating several componentsand subsystems of the fault tolerant computer system is provided. Thefault tolerant computer system may comprise a system board 182, abackplane board 184 which is interconnected with the system board 182,and a plurality of canisters 258, 260, 262, and 264 which interconnectwith the backplane board 184. A number ‘n’ of central processing units(CPUs) 200 are connected through a host bus 202 to a memory controller204, which allows for access to semiconductor memory by the other systemcomponents. In one presently preferred embodiment, there are four CPUs200, each being an Intel Pentium® Pro microprocessor. A number ofbridges 206, 208 and 210 connect the host bus to three additional bussystems 212, 214, and 216. The bus systems 212, 214 and 216, referred toas PC buses, may be any standards-based bus system such as PCI, ISA,EISA and Microchannel. In one embodiment of the invention, the bussystems 212, 214, 216 are PCI. In another embodiment of the invention aproprietary bus is used.

An ISA Bridge 218 is connected to the bus system 212 to support legacydevices such as a keyboard, one or more floppy disk drives and a mouse.A network of microcontrollers 225 is also interfaced to the ISA bus 226to monitor and diagnose the environmental health of the fault tolerantsystem.

The two PC buses 214 and 216 contain bridges 242, 244, 246 and 248 to PCbus systems 250, 252, 254, and 256. As with the PC buses 214 and 216,the PC buses 250, 252, 254 and 256 can be designed according to any typeof bus architecture including PCI, ISA, EISA, and Microchannel. The PCbuses 250, 252, 254 and 256 are connected, respectively, to a canister258, 260, 262 and 264. These canisters are casings for a detachable bussystem and provide multiple slots for adapters. In the illustratedcanister, there are four adapter slots. The mechanical design of thecanisters is described in more detail below in conjunction with FIG. 6.

The physical arrangement of the components of the fault tolerantcomputer shown in FIG. 2 are illustrated further in FIGS. 3A, 3B, and3C. Referring now to FIG. 3A, a chassis 170 is mounted on chassismounting rails 171 so as to be secured to the rack 102 of FIG. 1. Thechassis includes a front 170A, back 170B, sides 170C and 170D, as wellas a top 170E and a bottom 170F. Although not shown in FIG. 3A, sets ofperforations 177 in such patterns and numbers to provide effectivecooling of the internal components of the chassis 170 are also providedin its housing panels.

A central processing unit (CPU) module 103 which may advantageouslyinclude the system board 182 of FIG. 2 is removably mounted on achassis. A plurality of network interface modules 104 are also removablymounted on the chassis 170. The network interface modules 104 maycomprise the multiple-slot canisters 258, 260, 262, and 264 of FIG. 2.Two redundant power modules 105 are additionally removably mounted onthe chassis 170. The CPU module 103, the network interface modules 104,and the power modules 105, when removably mounted may have their frontspositioned in the same plane as the chassis front 170A.

In this embodiment, the CPU module 103 is removably mounted on the topchassis shelf 175A. The next chassis shelf 175B below holds tworemovably mounted network interface modules 104 and one removablymounted power module 105. The remaining chassis shelf 175C also holdstwo removably mounted network interface modules 104 and one removablymounted power module 105. The network interface modules 104 and thepower modules 105 are guided into place with the assistance of guiderails such as guide rail 180.

In one embodiment of the invention, the network interface modules 104and the power modules 105 are connected to the CPU module 103 through aninterconnection assembly module 209 (illustrated in additional detail inFIGS. 3B and 3C) which advantageously includes the backplane board 184illustrated in FIG. 2. The interconnection assembly module electricallyterminates and isolates the rest of the network server 100 from the PCBus local to any given network interface module 104 when that networkinterface module 104 is removed and replaced without powering down thenetwork server 100 or the CPU module 103. The physical layout of oneembodiment of the interconnection assembly module is described in moredetail below with reference to FIGS. 5A and 5B.

FIG. 3B illustrates the chassis 170 for the fault tolerant computersystem 170 in exploded view. With the interconnection assembly module209 installed in the rear, interconnection assembly module 209 mayprovide a communication path between the CPU module 103 and the networkinterface modules 104. In this embodiment, the interconnection assemblymodule 209 is mounted on the chassis back 170B such that it is directlybehind and mates with the chassis modules 103, 104 and 105 when they aremounted on the chassis 170.

Thus, with the interconnection assembly module 209 mounted on thechassis 170, the network interface modules 104 can be brought in and outof connection with the network server 100 by engaging and disengagingthe network interface module 104 to and from its associated backplaneboard connector. One embodiment of these connectors is described inadditional detail with reference to FIG. 3C below. This task may beperformed without having to power down the entire network server 100 orthe CPU module 103. The network interface modules 104 are thus hotswappable in that they may be removed and replaced without powering downthe entire network server 100 or the CPU module 103.

In FIG. 3C, a specific connector configuration for the interconnectionassembly module 209 is illustrated. As is shown in that Figure, fourconnectors 413, 415, 417, and 419 are provided for coupling torespective connectors of the network interface modules 104. Twoconnectors 421 are provided for the power modules 105. Another connector411 is configured to couple with the CPU module 103. The process ofinterconnecting the network interface modules 104 and the CPU module 103to the interconnection assembly module 209 is facilitated by guidingpegs 412, 414, 416, 418, 420 on the connectors of the interconnectionassembly module 209 which fit in corresponding guiding holes in thenetwork interface modules 104 and CPU module 103. The interconnectionassembly module 209 also includes two sets of perforations 422sufficient in number and in such patterns so as to assist with thecooling of each power module 105. This embodiment has two sets ofperforations 422 adjacent each power module connector 421.

FIG. 4 is a front view of the network server cabinet 101 housing apartially assembled fault tolerant computer system mounted on a rack102. In this Figure, the interconnection assembly module 209 is visiblethrough unoccupied module receiving spaces 201, 203, and 205. The CPUmodule 103 has not yet been mounted on the chassis as evidenced by theempty CPU module space 203. As is also illustrated in FIG. 1, severalnetwork interface modules 104 are present. However, one of the networkinterface modules remains uninstalled as evidenced by the empty networkinterface module space 201. Similarly, one power module 105 is present,but the other power module has yet to be installed on the chassis 170 asevidenced by the empty power module space 205.

In this Figure, the front of the interconnection assembly module 209mounted on the rear of the chassis is partially in view. FIG. 4 thusillustrates in a front view several of the connectors on the backplaneboard 184 used for connecting with the various chassis modules when thechassis modules are removably mounted on the chassis 170. As alsodescribed above, the CPU module 103 may be removably mounted on the topshelf 175A of the chassis in the empty CPU module space 203. As brieflyexplained above with reference to FIGS. 3A through 3C, the CPU module103 has a high density connector which is connected to the high densityconnector 411 on the back of the backplane printed circuit board 184when the CPU module is mounted on the top shelf 175A of the chassis 170.The chassis 170 and the guiding peg 412 assist in creating a successfulconnection between the 360 pin female connector 411 and the 360 maleconnector of the CPU module 103. The guiding peg 412 protrudes from thebackplane printed circuit board front and slip into correspondingguiding holes in the CPU module 103 when the CPU module 103 is mountedon the shelf 175A of the chassis 170.

In addition, one of the high density connectors 413 which interconnectsthe backplane printed circuit board 184 with one of the networkinterface modules 104 is shown in FIG. 4. In the illustratedembodiments, there are four high density connectors, one connecting toeach network interface module 104. The high density connector 413 may bea 180 pin female connector. This 180 pin female connector 413 connectsto a 180 pin male connector of the network interface module 104 when thenetwork interface module 104 is removably mounted on the middle shelf175B of the chassis in the empty network interface module space 201. Thechassis, the two guiding pegs (of which only guiding peg 414 is shown inFIG. 4), and the chassis guide rail 180 assist in creating a successfulconnection between the 180 pin female connector 413 and the 180 pin maleconnector of the network interface module 104. The two guiding pegs, ofwhich only guiding peg 414 is within view, protrude from the front ofthe backplane printed circuit board and slip into corresponding guidingholes in the network interface module 104 when the network interfacemodule 104 is removably mounted on a shelf of the chassis.

FIG. 5A is a view showing the front side of the backplane printedcircuit board 184. In this embodiment, the backplane printed circuitboard 184 is configured to be mounted on the chassis rear directlybehind the chassis modules comprising the CPU module 103, the networkinterface modules 104, and the power modules 105. The backplane printedcircuit board 184 may be rectangularly shaped with two rectangularnotches 423 and 424 at the top left and right.

As is also shown in FIG. 3C, the backplane printed circuit board 184also has high density connectors 413, 415, 417 and 419 which connect tocorresponding network interface modules 104. Each high density connectorhas a pair of guiding pegs 414, 416, 418, and 420 which fit intocorresponding guiding holes in each network interface module 104. Thebackplane printed circuit board also mounts a high density connector 411and a guiding peg 412 for connecting with the CPU module 103 and twoconnectors 421 for connecting with the power modules 105. The backplaneprinted circuit board 184 may also include sets of perforations 422sufficient in number and in such patterns so as to assist with thecooling of each power module 105. The perforations 422 are positioned inthe backplane printed circuit board 184 directly behind the powermodules 105 when the power modules 105 are removably mounted on theshelves 175B and 175C of the chassis.

FIG. 5B shows the rear side of the backplane printed circuit board 184.The back of the connectors 421 that connect to the connectors of thepower modules 105 are illustrated. Also, the rear of the high densityconnectors 413, 415, 417 and 419 which connect to the network interfacemodules 104 are also present on the backplane printed circuit board backto connect to the backplane printed circuitry. As shown in this Figure,each high density connector 413, 415, 417, 419 is attached to aninput/output (I/O) bus 341, 344, 349 or 350. In one advantageousembodiment, the I/O bus is a peripheral component interconnect (PCI)bus.

In one embodiment of the present invention, the I/O buses 341, 344, 349,and 350 are isolated by bus adapter chips 331, 332, 333 and 334. Thesebus adapter chips 331, 332, 333, and 334 provide, among other services,arbitered access and speed matching along the I/O bus. One possibleembodiment uses the DEC 21152 Bridge chip as the bus adapter 331, 332,333 or 334.

Several advantages of the present invention are provided by the busadapter chips 331 through 334 as they may be configured to provideelectrical termination and isolation when the corresponding networkinterface module 104 has been removed from its shelf on the chassis.Thus, in this embodiment, the bridge 331, 332, 333 or 334 acts as aterminator so that the removal and replacement of a network interfacemodule 104 from its shelf of the chassis 170, through an electricalremoval and insertion is not an electrical disruption on the primaryside of the bridge chip 331, 332, 333 or 334. It is the primary side ofthe bridge chip 331B, 332B, 333B or 334B which ultimately leads. to theCPU module 103. Thus, the bridge chip 331, 332, 333 or 334 providesisolation for upstream electrical circuitry on the backplane printedcircuit board 184 and ultimately for the CPU module 103 through anarbitration and I/O controller chip 351 or 352. As mentioned above, thisembodiment uses a PCI bus for the I/O bus. In such an instance, thebridge chip is a PCI to PCI bridge. The arbitration and I/O controllerchip 351 or 352 (not illustrated in FIG. 2 above) determines arbiteredaccess of the I/O bus and I/O interrupt routing. The I/O bus 343 or 346then continues from the arbitration and I/O controller chip 351 or 352to the back side of the high density connector 411 that connects withthe corresponding high density connector of the CPU module 103 when theCPU module 103 is mounted on the top shelf 175A of the chassis 170.

FIG. 6 shows aspects of one embodiment of a network interface module104. The modularity provided by the canister configuration provides easeof maintenance. Referring now to this Figure, the network interfacemodule 104 comprises a canister 560 with a front 560A, back 560B, sides560C, top 560D and bottom 560E. The canister front 560A may bepositioned proximate the front of the chassis when the canister isremovably mounted on a shelf of the chassis. A printed circuit board 561is secured flat against the canister side 560C inside the canister 560.The printed circuit board 561 comprises an I/O bus. As described above,in one advantageous embodiment, the I/O bus is a PCI bus. A plurality ofinterface card slots 562, are attached to the I/O bus. The number ofallowed interface card slots is determined by the maximum load the I/Obus can handle. In one illustrated embodiment, four interface card slots562 are provided, although more or less could alternatively be used.Also connected to the I/O bus and on one end of the printed circuitboard 561 is a high density connector 563 which mates with one of thehigh density connectors on the backplane board 184. Above and below theconnector 563 is a solid molding with a guiding hole. These two guidingholes correspond with a pair of guiding pegs 414, 416, 418, or 420 whichalong with the chassis and the chassis guiding rails assist, when thecanister 560 is removably mounted, in bringing together or mating the180 pin male connector 563 at one end of the printed circuit board 561and the 180 pin female connector 413, 415, 417 or 419 on the backplaneprinted circuit board 184.

Interface cards may be slipped into or removed from the interface cardslots 562 when the canister 560 is removed from its shelf 175B or 175Cin the chassis 170. An interface card slot 562 be empty or may be filledwith a general interface card. The general interface card may be anetwork interface card (NIC) such as, but not limited to, an Ethernetcard or other local area network (LAN) card, with a corresponding NICcable connected to the NIC and routed from the server 100 to a LAN. Thegeneral interface card may be a small computer system interface (SCSI)controller card with a corresponding SCSI controller card cableconnected to the SCSI controller card. In this embodiment, the SCSIcontroller card is connected by a corresponding SCSI controller cardcable to a data storage module which may be connected to data storagemodules such as hard disks 106 or other data storage device.Furthermore, the general interface card need not be a NIC or an SCSIcontroller card, but may be some other compatible controller card. Thecanister front 560A also has bay windows 564 from which the generalinterface card cable may attach to a general interface card. Unused baywindows may be closed off with bay window covers 565.

The network interface module 104 also has a novel cooling system. Eachnetwork interface module 104 extends beyond the chassis rear, and inthis portion, may include a pair of separately removable fans 566A and566B. The separately removable fans are positioned in series with oneseparately removable fan 566B behind the other separately removable fan566A. The pair of separately removable fans 566A and 566B run at reducedpower and reduced speed unless one of the separatey removable fans 566Aor 566B fails, in which case, the remaining working separately removablefan 566B or 566A will run at increased power and increased speed tocompensate for the failed separately removable fan 566A or 566B. Theplacement of the separately removable fans 566A and 566B beyond thechassis rear make them readily accessible from the behind the rack 102.Accessibility is desirable since the separately removable fans 566A and566B may be removed and replaced without powering down or removing thenetwork interface module 104.

To further assist with the cooling of the canister 560, the canister 560has sufficient sets of perforations 567 in such pattern to assist incooling the canister 560. In this embodiment, the perforations 567 areholes in the canister 560 placed in the pattern of roughly a rectangularregion.

A significant advantage of this embodiment is the ability to change ageneral interface card in a network server 100 without powering down thenetwork server 100 or the CPU module 103. To change a general interfacecard, it is desirable to first identify the bridge chip 331, 332, 333 or334 whose secondary side is connected to the network interface module104 containing the general interface card to be changed.

Assuming that the general interface card that needs to be changed is inthe network interface module 104 which is connected by PCI bus and highdensity connector to bridge chip 331, to remove the network interfacemodule 104 without disrupting operation of the other portions of theserver 100, the bridge chip 331 may become an electrical termination toisolate the electrical hardware of the network server from theelectrical removal or insertion on the bridge chip secondary side 331A.This may be accomplished by having the CPU module 103 place thesecondary side 331A, 332A, 333A or 334A of the bridge into a reset modeand having circuitry oil. the printed circuit board 561 of the networkinterface module 104 power down the canister 560 including the generalinterface cards within the canister 560. Once the canister 560 ispowered down and the bridge chip has electrically isolated the networkinterface module from the rest of the electrical hardware in the networkserver 100, then the network interface module 104 may be pulled out itsshelf 175B in the chassis; 170. After the network interface module 104has been removed, then the general interface card can be removed fromits interface card slot 562 and replaced. Subsequently, the networkinterface module 104 is removably mounted again on the shelf 175B in thechassis 170. The electrical hardware on the printed circuit board 561 ofthe network interface module 104 may then power up the canister 560including the general interface cards within the canister 560. Thebridge chip secondary side 331A, 332A, 333A or 334A is brought out ofreset by the CPU module 103 and the network interface module 104 isagain functional.

At no time during the procedure did the network server 100 or the CPUmodule 103 have to be powered down. Although the one network interfacemodule 104 was powered down during the procedure, the other networkinterface modules were still functioning normally. In fact, anyworkstation connected to the network server 100 by means other than theaffected network interface module 104 would still have total access tothe CPU module 103, the other network interface modules, and all thenetworks and data storage modules such as, but not limited to harddisks, CD-ROM modules, or other data storage devices that do not relyupon the general interface cards inside the removed network interfacemodule. This is a desired advantage since network server down time canbe very costly to customers and to vendors, can create poor customeropinion of the vendor, vendor's products and services, and decreaseoverall computing throughput.

The foregoing description details certain embodiments of the presentinvention and describes the best mode contemplated. It will beappreciated, however, that no matter how detailed the foregoing appearsin text, the invention can be practiced in many ways. As is also statedabove, it should be noted that the use of particular terminology whendescribing certain features or aspects of the present invention shouldnot be taken to imply that the broadest reasonable meaning of suchterminology is not intended, or that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated. The scope of the presents invention should therefore beconstrued in accordance with the appended Claims and any equivalentsthereof.

What is claimed is:
 1. A method of changing an interface card in acomputer, comprising: prior to removing a first interface module fromthe computer, powering down the first interface module via power controlcircuit without powering down said computer, such that the computer isprovided arbitrated access to at least a second interface module;removing the first interface module from the computer, comprising theact of electrically terminating and isolating electrical hardware ofsaid computer upstream the point where said first interface module isremoved; removing an interface card from said first interface module;replacing said interface card into said interface module; and replacingsaid first interface module into said computer without powering downsaid computer.
 2. A method as defined in claim 1 wherein said act ofremoving the interface module comprises the act of disconnecting a highdensity connector on said interface module from a high density connectoron said server when said interface module is removed from said server.3. A method as defined in claim 1 wherein said act of removing saidinterface card comprises the act of removing a network interface card(NIC).
 4. A method as defined in claim 1 wherein said act of removingsaid interface card comprises the act of removing a small computersystem interface (SCSI) controller card.
 5. A method as defined in claim1 wherein said act of removing said interface card comprises the act ofopening the interface module holding said interface card of said pluralinterface cards.
 6. A method as defined in claim 5 wherein said act ofopening the interface module comprises opening a canister.
 7. A methodas defined in claim 1 wherein said act of replacing said interfacemodule comprises the act of connecting a high density connector on saidinterface module to a high density connector on said server when saidinterface module is mounted on said server.
 8. A method as defined inclaim 1 wherein said act of replacing said interface module comprisesthe act of powering up said interface module including said pluralinterface cards after said interface module is replaced into saidserver.
 9. A method for interconnecting plural modules of a server,comprising: mounting a backplane printed circuit board on the back of achassis with a front, back, sides, top, and bottom; connecting a CPUmodule to said backplane printed circuit board when mounting a CPUmodule on said chassis; connecting each interface module of pluralinterface modules to said backplane printed circuit board when removablymounting each said interface module on said chassis, wherein saidbackplane printed circuit board comprises electrical hardware that isconfigured to provide electrical termination and isolation between saidinterface module and electrical circuitry on said backplane printedcircuit board upstream said electrical hardware when any of saidinterface modules has been removed; removably connecting at least oneinterface card to one of said plurality of interface modules; andremovably connecting a plurality of power modules to said backplaneprinted circuit board.
 10. A method as defined in claim 9 wherein theact of connecting said plural power modules to said backplane printedcircuit board comprises the act of connecting at least one redundantpower module of said plural power modules to said backplane printedcircuit board.
 11. A method as defined in claim 9 wherein said act ofconnecting said CPU module to said backplane printed circuit boardcomprises the act of connecting a high density connector of said CPUmodule to a high density connector of said backplane printed circuitboard.
 12. A method as defined in claim 9 wherein said act of connectingsaid CPU module to said backplane printed circuit board comprises theact of connecting a 360 pin male connector of said CPU module to a 360pin female connector of said backplane printed circuit.
 13. A method asdefined in claim 9 where said act of connecting said interface module tosaid backplane printed circuit board comprises the act of connecting ahigh density connector of said interface module to a high densityconnector on said backplane printed circuit board.
 14. A method asdefined in claim 9 where said act of connecting said interface module tosaid backplane printed circuit board comprises the act of connecting a180 pin male connector of said interface module to a 180 pin femaleconnector of said backplane printed circuit board.
 15. A method asdefined in claim 9 wherein said act of connecting said interface moduleto said backplane printed circuit board comprises the acts of poweringup said interface module and commanding electrical hardware on saidbackplane printed circuit board to stop acting as an electricaltermination and to stop isolating electrical hardware of said backplaneprinted circuit board from the electrical hardware of said interfacemodule.
 16. A method as defined in claim 15 wherein said act of poweringup said interface module comprises the act of powering up plural generalinterface cards therein.
 17. A method as defined in claim 9 furthercomprising the act of connecting by cable plural data storage modules toa interface module of said plural interface modules.
 18. A method asdefined in claim 9 wherein the backplane printed circuit board furthercomprises electrical hardware that is configured to provide arbitratedaccess to said interface module.